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Thyroid hormone (T3) stimulates various metabolic pathways and the hepatic actions of T3 are mediated primarily through the thyroid hormone receptor beta (TRβ). Hypothyroidism has been linked with low grade inflammation, elevated risk of hepatic steatosis and atherosclerosis. Secretory phospholipases (sPLA2) are associated with inflammation, hyperlipidemia and atherosclerosis. Due to potential linkage between thyroid hormone and sPLA2, we investigated the effect of thyroid hormone status on the regulation of secretory phospholipases in mice, rats and human liver. T3 suppressed the expression of the sPLA2 group IIa (PLA2g2a) gene in the liver of BALB/c mice and C57BL/6 transgenic mice expressing the human PLA2g2a. PLA2g2a was elevated with hypothyroidism and high fat diets which may contribute to the low grade inflammation associated with hypothyroidism and diet induced obesity. We also examined the effects of the TRβ agonist eprotirome on hepatic gene regulation. We observed that eprotirome inhibited the expression of selected sPLA2 genes and furthermore the cytokine mediated induction PLA2g2a was suppressed. In addition, eprotirome induced genes involved in fatty acid oxidation and cholesterol clearance while inhibiting lipogenic genes. Our results indicate that in vivo thyroid hormone status regulates the abundance of sPLA2 and the inhibition of PLA2g2a by T3 is conserved across species. By regulating sPLA2 genes, T3 may impact processes associated with atherosclerosis and inflammation and TRβ agonists may ameliorate inflammation and hyperlipidemia.  相似文献   
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Many insects undergo diapause to survive adverse seasons. Although the mechanism of diapause induction is the subject of extensive study, that of diapause termination remains poorly understood. In the present study, we show the endocrine processes leading to the termination of pupal diapause in Mamestra brassicae. Diapause of this insect is terminated if the pupae are exposed to a low temperature for several weeks. During this period, the prothoracic glands (PGs) of pupae acquire the potential to secrete sufficient ecdysteroids necessary for inducing adult development. The main endocrine changes observed under the low temperature conditions are: (i) the increase in activity of the PGs in two steps; (ii) the increase in responsiveness of the glands to prothoracicotropic hormone (PTTH); and (iii) two‐step increase in PTTH gene expression in the brain. The timing of the first and second increases in PG activity roughly coincides with that of the two steps of increase in PTTH gene expression, and the timing of the increase in the responsiveness of the PGs to PTTH coincides with the second, larger increase in PTTH gene expression. The ablation of the PGs prior to cooling pupae does not affect the increase in PTTH gene expression, whereas brain removal results in a failure to increase PG activity, strongly suggesting that PTTH is the master regulator of diapause development and termination.  相似文献   
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A partial swine cDNA which encodes the functional domain of PIT-1 was isolated by the polymerse chain reaction (PCR). The swine PIT-1 cDNA clone is 95% identical at the protein level to the rat Pit-1 gene. Thus, Pit-l's known function in control of rat growth hormone and prolactin expression is likely to be conserved in swine. This swine cDNA clone was used to investigate genetic variability at PIT-1 in several American and Chinese breeds. Polymorphic BamIII fragments were found in pure-bred Meishan animals (n= 13), but only monomorphic fragments in five American breeds (n= 36).  相似文献   
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The effects of a high-growth genetic background on the growth of mice hemizygous for one of two growth hormone transgenes were examined. Male mice hemizygous for wild-type (W) and dwarf mutant (M) bovine growth hormone (bGH) transgenes were crossed with females of a high-growth selected (S) and control (C) line as follows: W x S, W x C, M x S and M x C. Body weights of progeny were recorded weekly from 2 to 10 weeks of age. F1 progeny were classified as carriers (P) or non-carriers (N) of the transgene by assaying tail DNA for bGH using the polymerase chain reaction and agarose gel electrophoresis. A deficiency in the number of f1 progeny carrying the W (P<0.05) and M (P<0.01) bGH transgene was most likely due to differential prenatal and early postnatal mortality. Bodyweight means of wild-type transgenic mice were larger (P < 0.05) than those of non-transgenic littermates by 3 weeks of age in a C background in contrast to 5 weeks in S. The wild-type bGH transgene increased adult body weights more in the C (155%) than in the S (136%) background, indicating transgene expression by selection background interaction (P < 0.05). However, the growth response to the wild-type transgene in the S background was still large. The dwarf mutant transgene had a greater effect on growth reduction in the S (70%) than in the C (84%) background, thus causing transgene expression by selection background interaction (P < 0.05). Gender by wild-type transgene effect interactions (P < 0.001) for adult body weight were caused by the transgene reducing the gender difference for body weight in C and eliminating it in S. The dwarf mutant caused a larger negative effect on growth in males than in females, resulting in a gender by dwarf mutant transgene interaction (P < 0.001) for adult body weights. Results indicate that the effect of a GH transgene on growth can be affected both by a high-growth genetic background and the gender of progeny.  相似文献   
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The purpose of the present work was to develop a chromatographic system for the separation of five molecular forms of the gonadotropin-releasing hormone (GnRH); mammalian GnRH (mGnRH) (LHRH), salmon GnRH (sGnRH), chicken I GnRH (clGnRH), chicken II GnRH (cIIGnRH) and lamprey GnRH I (IGnRH-I). By using an ion-exchange HPLC column and isocratic elution, it was possible to separate properly the five peptides in approximately 20 min. The utility of the system in determining the GnRHs forms present in the brain of two species of vertebrates was examined.  相似文献   
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Previous work from our laboratory provided evidence for increased plasma corticosterone levels in mice transgenic for human and bovine growth hormone (GH). Corticosterone was elevated in both sexes, under both basal and ether-induced stress conditions. The objectives of the present study were to investigate thein vitro adrenal sensitivity to ACTH, GH and/or IGF-I in normal and bGH transgenic mice, to examine plasma corticosterone levels at different times of the day, and to determine plasma levels of ACTH in these animals. For the measurement of plasma corticosterone and ACTH levels, transgenic and normal siblings were housed 2 per cage and decapitated simultaneously within 20 seconds of the first disturbance of the cage. The corticosterone production byin vitro adrenal incubations did not differ between adrenals from normal and transgenic mice at the basal level or in the presence of different doses of ACTH. Growth hormone or IGF-I did not have any effect on corticosterone productionin vitro when given alone, and did not modify the effects of ACTH on the accumulation of corticosterone in the media. Plasma corticosterone concentrations were higher in transgenic than in normal animals in both morning and evening. Plasma concentrations of ACTH in animals killed in the morning were sharply increased in transgenic males as compared with their normal siblings. The results indicate that increased circulating levels of corticosterone in transgenic mice are not due to a potentiation of ACTH actions by GH or IGF-I, but rather to a chronic increase in plasma ACTH levels. The increase in ACTH is presumably a reflection of GH actions in the hypothalamic-pituitary system.  相似文献   
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Abstract Isolation and identification of allatostatin 4 (AST 4) from crude brain extracts of female Diploptera punctata are described. Synthetic analogues of allatostatin 4 truncated from the N-terminal were evaluated to gain some knowledge of structure-activity correlation. AST 4 reversibly inhibits the biosynthesis of JH in vitro . AST 4 has the following sequence: Asp-Arg-Leu-Tyr-Ser-Phe-Gly-Leu-NH2. This neurohormone (AST 4) has no sequence similarity with any known neuropeptide from other organisms. Synthetic AST 4 as well as truncation fragments, including two with the five and six amino acids terminal residues deleted showed in vitro activity distinguishable from that of the native allatostatin.  相似文献   
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